1. Field of the Invention
The present invention generally relates to locking mechanisms and, in particular, to a specialized lock for securing a clamping device.
2. Description of the Prior Art
The prior art is rife with examples of locking devices. Many attempts have been made to overcome wear problems where positive locking is required, for example, in airplane landing gear. Further, very complex locking devices are disclosed in the art. U.S. Pat. No. 2,713,328 of Driskel et al positions and locks an internal shaft by the provision of a raised portion on the shaft and a series of balls positionable in indentations in the raised portion. The lock is actuated selectively, and depends upon the operation of a clamp device external to the rod. This type of unit is subject to wear, and adjustment is not possible due to the contact between the indentations, the balls, and the clamp. Thus, there is a need in the art for units in which wear of the component parts can be at least partially compensated for, for example, by adjusting the position of the locking portion at the time of locking.
One method of taking care of this particular wear problem is disclosed by Firestone in U.S. Pat. No. 3,208,759. In this patent, a collet seal utilizes a base and lip on the inner cylinder as the contact points for the balls, and maintains them in close contact with a slideable member which contacts the lip on the cylinder. This type of unit, however, does not provide positive locking, although it does overcome the problem of gradual deterioration and wear, and thus looseness in the ball area.
Another method of overcoming the loss of tight sealing is disclosed in U.S. Pat. No. 3,397,620 of Skelton et al. In this reference, spring loading is provided to position the locking balls, and the shaft to be locked is further spring loaded. However, this type of system has the drawback of wear by repeated use of the springs, and the possibility that external forces would overcome the effect of the springs, independent of the fluid loading system.
Cruse in U.S. Pat. No. 3,324,771 discloses a friction operating mechanism with locking means. In this system, separate springs of differing characteristics are utilized and positioned in such a manner that one of them is compressed at all times. Locking is effected by pivoted members that contact a lip on the center of an inner piston. This type of system overcomes some of the above problems in that it provides for a positive lock and compensates for wear. However, the use of opposed springs presents a different problem, i.e., that of possible spring breakage or loss of pressure due to use.
One system of overcoming the opposed spring type of problem is disclosed in U.S. Pat. No. 3,584,544 to Haberman, in which a single spring is used to load a central piston, and positive locking is effected by shaped rollers and keys. However, this system still requires the use of at least one spring to place tension upon the locking portion of the system and must be utilized in conjunction with a large contact surface roller which would be subject to wear and eventual positive locking problems. R. H. Royster in U.S. Pat. No. 3,107,582 discloses another system similar to that of Haberman. However, instead of using rollers, Royster utilizes radially oriented rods having specific cut out portions on the upper and lower surfaces thereof. This type of unit thus suffers from the same spring wear problems as the other prior art, and the above wear problems when dealing with locking by a rod.
It is another object of the present invention to provide a simple locking mechanism that does not depend upon flui pressure to retain a predetermined position.
It is further object of the present invention to provide such a locking device in a very simple, easy to construct form.